Visiting Vet: Giardia

Puppies may have a 30 to 50 percent chance of having giardia. —Wiki commons

Tijax, a bouncy golden retriever puppy, belongs to an exceptionally knowledgeable owner who gives her new companion state-of-the-art healthcare. She educates herself about each recommendation, then follows through faithfully. Every dog should have such an attentive parent … but I live in fear of missing or forgetting something about which my erudite client will then inform me. Seriously, it’s a veterinarian’s dream to have pet owners this intelligent and involved in their animals’ well-being, letting us practice “gold standard” medicine all the time. So something happened recently with Tijax that highlighted the dilemma veterinarians often face about even basic preventive healthcare. It has to do with poop, so no adolescent snickering, please.

The Companion Animal Parasite Council (CAPC) is an independent council of veterinarians, veterinary parasitologists, and other animal healthcare professionals which publishes guidelines for veterinarians about all things parasitic. When it comes to canine intestinal parasites, they advise, “Conduct fecal examinations at least four times during the first year of life, and at least two times per year in adults, depending on patient health and lifestyle factors.” Now, I know my clients. About half remember to bring stool samples to their annual appointments. The rest often let me “collect” samples … straight from Fido, using an exam glove. Those who say, “I’ll drop a sample off later,” almost never do. I get it. It’s not the most pleasant task. So, bottom line, Fido’s lucky if we run one fecal test annually. Forget about twice. Four times? Um … not likely.

Then there are the people who insist, “Fido doesn’t need that test. His poop looks fine. I don’t see any worms.” That’s where educating yourself would come in handy. It’s a common misconception that intestinal parasites are visible in the feces. Most worms infecting dogs stay happily in the gut, never seeing the light of day. Dogs are also susceptible to several microscopic protozoal parasites. When we send a sample for testing, first the lab performs a special concentrating technique and examines for microscopic worm eggs and protozoal bugs. Then they run a recently developed enzyme-linked immunosorbent assay (ELISA), which tests for substances called antigens that are secreted by adult worms into Fido’s feces. The ELISA test diagnoses cases in which the worms are not laying eggs, thus catching a significant number of infections missed by the first test.

Consider Tijax. She had been given deworming medication by the breeder prior to arriving on the Vineyard. Once here, we had submitted one sample to the lab, which had come back clear. Tijax’s mom was totally on board for following guidelines, so when advised, brought another sample. This time, the lab found many giardia cysts.

Giardia are protozoal parasites that can affect dogs, cats, rodents, cattle, some wild mammals, and people. There are a variety of species, though they are difficult to distinguish from one another, and all have similar life cycles. First, a mobile form called a trophozoite lives in the intestines of infected hosts. Under the microscope, a trophozoite looks like a funny, pear-shaped face, with two eyes, goofy smile, and long tail that helps it swim slowly around in a way that has been described as a “falling leaf” motion. When trophozoites pass out of the host’s body in the poop, they quickly morph into microscopic cysts. This can happen within hours. Each cyst contains two “sleeping” trophozoites. These cysts are tough, surviving for months outside in all types of environments, just waiting for Tijax to come along and swallow them. Maybe she laps them up in contaminated water. That’s one of the most common modes of transmission. Perhaps she wanders through a fecal-laden dog park, then goes home and licks her muddy paws. Once inside our furry friend, the shell of the cyst gets digested, and trophozoites are released into her intestines. They swim around, eventually attaching to the intestinal wall with a little apparatus like a suction cup, where they stay until they ultimately pass in the feces, turn to cysts, and the cycle begins again.

Diagnosis can be tricky. Trophozoites and cysts are not always being shed. It took repeated tests for us to diagnose Tijax’s infection. And like Tijax, many infected animals do not have any clinical signs. In asymptomatic animals, giardia may actually be considered normal intestinal microflora. When dogs do get sick, the primary symptom is diarrhea. Some sources estimate 10 percent of pet dogs may be infected with giardia. For puppies, that may go up to 30 to 50 percent. For shelter dogs, maybe even 100 percent. In my experience, those estimates seem high, but it probably varies with the part of the country, and level of pet care provided. Puppies are certainly more susceptible. People can also be infected with certain species of giardia. Since we usually can’t determine whether the type diagnosed in a pet is one that can also affect people, it just makes sense to always practice good sanitation. In other words, wash your hands!

If Tijax doesn’t have diarrhea, and infection might be considered “normal,” when and why do we treat? Most veterinarians agree it makes sense to treat puppies, even if they don’t have the runs, to eliminate the parasite. Just because there’s no diarrhea today doesn’t mean there won’t be tomorrow. Diarrhea happens. Besides, infection may interfere with absorption of vitamins and nutrients. We also want to avoid transmission to other pets and people. The problem is, we don’t always successfully eliminate giardia, even with multiple treatments. In older asymptomatic dogs, I discuss human health risks with owners, maybe treat once or twice, but rarely worry if an otherwise healthy dog continues to test positive. In Tijax’s case, we are treating her, testing other household pets, and minimizing environmental contamination. Since giardia cysts can stick to Tijax’s fur, a bath is also planned. We will recheck a third fecal sample in two to four weeks … because Tijax’s mother gets it. She understands the science, and choses to provide optimum care. Thanks, Mom!